Cartesianism is the school of philosophy based on the fundamental philosophical principles of the great French philosopher René Descartes. Descartes lived from 1596 to 1650, and published his major philosophical works, Discourse on Method, Meditations on First Philosophy, and Principles of Philosophy, in 1637, 1641, and 1644 (respectively). At the time, the dominant philosophical school was that of Scholastic (Aristotelian) philosophy. Descartes studied Scholastic philosophy, and become deeply dissatisfied with it at a very young age. Believing that all human knowledge could be either reinforced or polluted by philosophical principles on which it rested, Descartes resolved to establish a new philosophical system from the ground up.
Though, contrary to Descartes' hopes, his philosophy was poorly received by the existing educational institutions, Descartes' work exercised an enormous influence throughout Western Europe. Even today, his Meditations is often taken as the starting point for modern philosophy. The great thinkers of the seventeenth and eighteenth centuries (Locke, Spinoza, Leibniz, Kant, and others) can all be mapped on the basis of their reactions to Descartes' system. Because his thoughts inspired such dramatic resistance and development among those thinkers, however, the fact is often overlooked that in the decades following his major publications, a large number of philosophers devoted themselves to understanding and defending his philosophy.
This article focuses on the three issues of central philosophical interest to the Cartesians. It does not discuss one of the major points of Cartesian concern: the development of Descartes' physics. While that physics was an extremely important step between Aristotelian and Newtonian physics (Newton himself made a close study of Descartes' physics, and much of his work is an explicit response to it), it is of limited philosophical interest.
While Descartes himself went to great lengths to distance his philosophical system from the then-dominant Scholastic philosophy, he nevertheless hoped that his views would be adopted by the educational and religious establishment (indeed, he advertised the Meditations as primarily a proof of the existence of God and the immortality of the soul). Though the works spread like wildfire among the intellectual community (in large part due to his acquaintance with Marin Mersenne, the central figures of the establishment unequivocally rejected them.
In light of this, one of the tasks many of Descartes' followers set themselves was finding ways to bring the Cartesian system closer to the Scholastic. Sometimes this happened simply on a presentational level. Scholastic philosophy was typically presented in a specific format, one based in the classic ordering of Aristotle's texts. Descartes' own works, even the carefully ordered Principles of Philosophy had little in common with this format. Because of this, many of his followers worked at producing textbooks of Cartesian philosophy that closely resembled existing Scholastic textbooks.
In other instances, Cartesians took on the more ambitious task of attempting to reconcile the philosophical content of the two systems. Johannes Clauberg, for instance, published treatises on logic and metaphysics that attempted to provide a Cartesian foundation for the Scholastic system. Later, Leibniz, in the development of his own philosophical system, continued in this vein, attempting to show that both Cartesianism and Scholasticism contained elements of truth that could be unproblematically integrated.
Central to Descartes' view of the universe was his claim that the mind and the body were distinct, independent substances of radically different natures. His arguments for this view were well received, and are still the subject of much discussion (see Philosophy of Mind). However, this dualist doctrine faced a problem: that of mind-body interaction. Intuitively, our minds and bodies are in regular causal interaction. For instance, our decisions cause our bodies to move, and sharp objects' collisions with our bodies cause sensations of pain in our minds. But this intuitive fact stands in tension with the idea that the mind and body are of fundamentally different natures. Descartes himself asserted that, however difficult to understand, this simply was how things stood.
Some of Descartes' followers (including Nicolas Malebranche, Louis de La Forge and Arnold Geulincx) believed that another part of Descartes metaphysical doctrine pointed towards, or even committed Descartes to, a solution to the problem. In one of his proof for the existence of God, Descartes asserted that finite beings such as himself lacked the power to continue their own existence from one moment to the next. From this, he concluded that the persistence of all finite beings required the causal support of an infinite being, namely God. This doctrine was often read as stating that God recreated the universe at every moment in time.
With that view in mind, consider an apparent instance of causation. Say that one billiard ball collides with another, after which the other rolls away. If God were recreating the universe each moment, though, it would seem that, strictly speaking, there were no objects that were around long enough throughout that event in order to stand in causal interaction. Really, all the causal features of the event came from God, whose choice it was to create things as they were at each moment. In other words, God was the only causal force involved. The other features of the situation were merely the occasions on which God exercised his causal power. Generalized, this is the position known as "occasionalism."
Returning to the apparent interaction of the mind and mind, the occasionalists were able to hold to the doctrine that the mind and body were of utterly different natures, and accept the claim that things of radically different natures are unable to interact. The apparent interaction is then an appearance resulting from God's, independently affecting the mind and body. For instance, your decision to reread a sentence does not cause your eyes to move back up the page—rather, that decision is just the occasion on which God causes your eyes to move back up the page.
From a contemporary philosophical perspective, one of the most interesting debates to emerge among the Cartesians concerned the nature of the ideas in our minds. Central to Descartes' theory was the notion of "clear and distinct ideas." These ideas, he argued, are guaranteed by God to be veridical, and so can form the starting point for an unshakeable philosophical system. Put more loosely, these ideas were guaranteed to be accurately getting at reality.
However, Descartes' proof of the claim that our clear and distinct ideas are veridical was met with suspicion. Antoine Arnauld and others noticed that the proof appeared to rely on certain ideas about the nature of God, but that the reason these ideas were taken to be accurate was that they were clear and distinct. In other words, Descartes appeared to be arguing in a circle: assuming the veridicality of clear and distinct ideas in order to prove their veridicality.
The Cartesians wanted to retain the ability to base their system on necessarily veridical ideas. One approach to doing so, in light of the worries about Descartes' proof, was to offer different accounts of the nature of those ideas. Descartes held that clear and distinct ideas were modifications of our minds - entities that subsisted in our minds, and were dependent only on our minds for their existence. This view, however, opens the door to worries about the ideas' accuracy: for if the ideas depend for their existence only on our minds, then it appears that we would have the same ideas regardless of how the world was around us. But in that case, the ideas' link to reality is not a matter of necessity.
Nicolas Malebranche offered what he took to be a refinement of Descartes' views that addressed this problem. He held that when we have a clear and distinct idea, we are actually conscious of ideas in the mind of God. Through his link with us, God is able (at times) to provide us such access. But these ideas are God's own ideas of the world, the ideas on which his act of creation (and, as the occasionalists saw it, his continual acts of recreation) depended. They are therefore guaranteed to be accurate.
Arnauld strongly and publically attacked Malebranche's theory, both as a refinement of Descartes' view and on its own philosophical merits. He held that ideas are modications of the mind only in the sense that they are the form of a certain mental act, whereby the mind stands in some direct relation to objects. It is not the case, he claimed, that we are somehow stuck behind a "veil of ideas," whether ideas in our own minds or in God's mind. What we perceive and think about are the actual objects we always took ourselves to be perceiving or thinking about.
This debate is seen as one of the clearest forerunners to the contemporary debate in the philosophy of perception between so-called "direct" and "indirect" theories of perception.
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